[meteorite-list] Source of Zodiac Glow Identified

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 16 Apr 2010 13:12:27 -0700 (PDT)
Message-ID: <201004162012.o3GKCROl018069_at_zagami.jpl.nasa.gov>

April 15, 2010
 
Contacts:
Maria Martinez
Southwest Research Institute
+1 (210) 522-3305
mmartinez at swri.org
 
Karen Randall
SETI Institute
+1 (650) 960 4537
krandall at seti.org
 
SOURCE OF ZODIAC GLOW IDENTIFIED
 
The eerie glow that straddles the night time zodiac in the eastern sky
is no longer a mystery. First explained by Joshua Childrey in 1661 as
sunlight scattered in our direction by dust particles in the solar
system, the source of that dust was long debated. In a paper to appear
in the April 20 issue of The Astrophysical Journal, David Nesvorny and
Peter Jenniskens put the stake in asteroids. More than 85 percent of
the dust, they conclude, originated from Jupiter Family comets, not
asteroids.
 
"This is the first fully dynamical model of the zodiacal cloud," says
planetary scientist Nesvorny of the Southwest Research Institute in
Boulder, Colo. "We find that the dust of asteroids is not stirred up
enough over its lifetime to make the zodiacal dust cloud as thick as
observed. Only the dust of short-period comets is scattered enough by
Jupiter to do so."
 
This result confirms what meteor astronomer Jenniskens of the SETI
Institute in Mountain View, Calif., had long suspected. An expert on
meteor showers, he had noticed that most consist of dust moving in
orbits similar to those of Jupiter Family comets, but without having
active dust-oozing comets associated with them.
 
Instead, Jenniskens discovered a dormant comet in the Quadrantid
meteor shower in 2003 and has since identified a number of other such
parent bodies. While most are inactive in their present orbit around
the Sun, all have in common that they broke apart violently at some
point in time in the past few thousand years, creating dust streams
that now have migrated into Earth's path.

Nesvorny and Jenniskens, with the help of Harold Levison and William
Bottke of the Southwest Research Institute, David Vokrouhlicky of the
Institute of Astronomy at Charles University in Prague, and Matthieu
Gounelle of the Natural History Museum in Paris, demonstrated that
these comet disruptions can account for the observed thickness of the
dust layer in the zodiacal cloud.
 
In doing so, they solved another mystery. It was long known that snow
in Antarctica is laced with micro-meteorites, some 80 to 90 percent of
which have a peculiar primitive composition, rare among the larger
meteorites that we know originated from asteroids. Instead, Nesvorny
and Jenniskens suggest that most antarctic micro-meteorites are pieces
of comets. According to their calculations, cometary grains dive into
Earth's atmosphere at entry speeds low enough for them to survive,
reach the ground, and be picked up later by a curious micro-meteorite
hunter.
 
 ?????????????????????????? # # #
 
This work was funded by the NASA Planetary Geology and Geophysics
Program and the NASA Planetary Astronomy programs.
 
An image to accompany this story is available:
http://www.swri.org/press/2010/Comet.htm
 
More information:
http://cams.seti.org
Received on Fri 16 Apr 2010 04:12:27 PM PDT


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